Thank you for bringing this up. They are definitely a solid group, but look at their division... Kaep who is an awful throwing QB... Carson Palmer who is past his prime and a turnover machine (Sherman had two of his INT's vs. him in week 15, Hawks still lost...), and Kellen Clemens played Seattle twice this year.
Seattle hasn't really been tested by a good offense except vs. Indy (Loss), Houston (won in OT after Schaub threw a pass right to Sherman during his 4 straight games of throwing a pick 6), and New Orleans. They beat up on NO pretty good but both games were at Seattle in tough conditions and bad weather favoring the defense. Andre Johnson and Marquis Colston both logged very nice days vs. the Seahawks secondary.
Everybody keeps bringing up their pass rush too. Yes, they can rush the passer but are they phenomenal at it? No. They've average 2 sacks a game the past four games.
Seattle seems like KC, only with better DB's and a worse offense. Eliminate their home field advantage and they seem very vulnerable.